Wind turbines for generating electric power normally comprise a vertical support; a main frame which rotates about a vertical axis with respect to the vertical support; a blade assembly, which comprises a hub and at least two blades fitted to the hub, and is connected to the main frame by at least one bearing to enable the blade assembly to rotate about a rotation axis; and a rotating electric machine rotated by the blade assembly and comprising a stator connected to the main frame, and a rotor connected to the blade assembly. The stator and rotor normally comprise respective tubular active parts facing each other and separated by an air gap.
The blade assembly on direct-drive wind turbines is connected rigidly to the rotor, and the bearing supports both the rotor and the blade assembly for rotation about the rotation axis. On direct-drive wind turbines, it is a fairly common practice to employ one bearing to absorb radial and axial forces and tipping moments. Whereas other wind turbine configurations employ two coaxial bearings. Each active part is usually divided into active segments fitted to a respective tubular structure and extending predominantly axially with respect to the rotation axis of the rotating electric machine.
Installing the wind turbine and servicing the rotating electric machine both involve assembling and/or disassembling the active segments of the rotating electric machine in a position that makes it relatively difficult to insert and/or extract and handle the active segments.